1. Field of the Invention
This invention relates generally to apparatus for supporting a magnetic transducer or head, and has particular application to a video tape recorder (VTR) in which stop-motion, slow-motion or fast-motion pictures as well as normal-motion pictures can be reproduced.
2. Description of the Prior Art
In a conventional VTR, a rotary transducer or head assembly is provided with one or more magnetic transducers which scan successive parallel tracks on a magnetic tape so as to record and/or reproduce video signals in such tracks. In general, while the one or more transducers or heads rotate so as to scan across the tape, the tape itself is transported longitudinally. In a typical so-called helical scan VTR, each transducer or head is mounted on a rotary portion of a guide drum so as to scan magnetic tape which is helically wrapped about at least a portion of the circumference of the guide drum. During recording, a tracking servo system controls the rotation of the one or more transducers with respect to the tape movement, and control pulses are recorded on a marginal portion of the tape. During normal reproduction, the same or a similar servo system is used to synchronize the movement of the tape in respect to the rotation of the transducers based on the reproduced control pulses, whereby the scanning path of each of the heads or transducers is made to coincide with one of the previously recorded tracks and an accurate video picture can be displayed in response to the reproduced video signal.
Recently, VTRs have been provided which are capable of various modes of reproducing operation, such as, "stop or still-motion", "slow-motion" and "quick or fast-motion" reproducing operations, in addition to the normal reproducing mode. In these various reproducing modes other than the normal mode, the tape speed differs from the speed during recording. Consequently, the scanning path of each head or transducer is inclined, or angularly disposed, with respect to the directions of the recorded tracks. By reason of the foregoing, in the various reproducing modes other than the normal mode, guard band noise or crosstalk will result from the tracking errors or inclination of the scanning paths of the heads relative to the recorded tracks.
It has been proposed, for example, in U.S. Pat. No. 4,080,636, to correct such tracking errors in the scanning path of each rotary head or transducer by mounting the latter at the free end of a cantilevered support member in the form of a so-called bi-morph leaf which is normally planar and flexes arcuately along the entire length of the support member in a direction, and by an amount depending upon the polarity and amplitude of an electrical drive signal applied thereto. Moreover, the bi-morph leaf is oriented and the drive signal applied thereto is suitably controlled so as to deflect the transducer supported thereby in directions that are transverse or perpendicular in respect to the plane of rotation of the head or transducer, and hence lateral in respect to the directions of the record tracks, whereby to cause the head scanning path to coincide with the record track being scanned thereby. Although tracking errors are minimized or avoided by the use of a suitably controlled bi-morph leaf for supporting the transducer or head, as aforesaid, it will be appreciated that arcuate flexing of the bi-morph leaf for deflecting the head mounted at its free end laterally in respect to a record track being scanned causes the active face of the head, that is, the surface of the transducer or head at which the usual gap is provided, to deviate angularly from the tape surface. At the extremes of the lateral deflection of the head, the contact angle error or angular deviation of the active face of the magnetic transducer or head in respect to the surface of the tape or other record medium substantially reduces the signal coupling and, thereby, adversely affects the stability of the reproduced picture.
In order to avoid the foregoing problem, it has been proposed, for example, in U.S. Pat. No. 4,099,211, to form the cantilevered support member for the magnetic transducer or head of independently deflectable inner and outer bi-morph leaf elements having opposite polarizations and being crosswired so as to be flexed in opposite or reverse directions upon application of the electrical drive signal thereto. By reason of the foregoing arrangement, the contact angle error or inclination of the active face of the transducer or head in respect to the record medium surface may be decreased, or even eliminated as the transducer or head is deflected in a direction extending laterally to its plane of rotation. However, the manufacture of such cantilevered support members composed of inner and outer, oppositely polarized bi-morph elements, and the crosswiring thereof are undesirably complex and costly.
Further, in mounting a magnetic transducer or head on a bi-morph leaf for deflection of the head laterally in respect to its plane of rotation upon flexing of the bi-morph leaf, difficulties are encountered in affixing the transducer or head to the bi-morph leaf at a region of the latter at which such flexing occurs. Moreover, in cases where the cantilevered support member for the magnetic transducer or head is formed of one or more bi-morph leaf elements, as aforesaid, the support member tends to be relatively heavy, particularly adjacent its free end carrying the transducer or head so that the resulting head assembly has a relatively slow response to rapid changes in the electrical drive signal.